// Copyright (c) 2013, The Toft Authors. All rights reserved.

// From http://www.azillionmonkeys.com/qed/hash.html

#include "toft/hash/super_fast.h"

namespace toft {

#undef get16bits
#if (defined(__GNUC__) && defined(__i386__)) || defined(__WATCOMC__) || \
    defined(_MSC_VER) || defined(__BORLANDC__) || defined(__TURBOC__)
#define get16bits(d) (*((const uint16_t *) (d)))
#endif

#if !defined (get16bits)
// NOLINT(readability/casting)
#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
                         +(uint32_t)(((const uint8_t *)(d))[0]) )
#endif

uint32_t SuperFastHash(const char * data, int len) {
    uint32_t hash = len, tmp;
    int rem;

    if (len <= 0 || data == NULL)
        return 0;

    rem = len & 3;
    len >>= 2;

    /* Main loop */
    for (; len > 0; len--) {
        hash += get16bits(data);
        tmp = (get16bits(data + 2) << 11) ^ hash;
        hash = (hash << 16) ^ tmp;
        data += 2 * sizeof(uint16_t); // NOLINT(runtime/sizeof)
        hash += hash >> 11;
    }

    /* Handle end cases */
    switch (rem) {
    case 3:
        hash += get16bits(data);
        hash ^= hash << 16;

        // Treat the final character as signed. This ensures all platforms behave
        // consistently with the original x86 code.
        // NOLINT(runtime/sizeof)
        hash ^= static_cast<signed char>(data[sizeof(uint16_t)]) << 18;
        hash += hash >> 11;
        break;
    case 2:
        hash += get16bits(data);
        hash ^= hash << 11;
        hash += hash >> 17;
        break;
    case 1:
        hash += static_cast<signed char>(*data);
        hash ^= hash << 10;
        hash += hash >> 1;
    }

    /* Force "avalanching" of final 127 bits */
    hash ^= hash << 3;
    hash += hash >> 5;
    hash ^= hash << 4;
    hash += hash >> 17;
    hash ^= hash << 25;
    hash += hash >> 6;

    return hash;
}

}  // namespace toft
